1. Field of Invention
The present invention relates generally to electrohydrodynamic printing and more specifically, but not by way of limitation, to nozzles for electrohydrodynamic printers.
2. Description of Related Art
Examples of electrohydrodynamic printer nozzles are disclosed in U.S. patent application Ser. No. 12/713,886 and U.S. patent application Ser. No. 12/669,287.
Electrohydrodynamic (EHD) printing is a highly versatile printing technology that can provide printing resolutions in the micron to submicron range. EHD printing generally uses a strong electric field to eject printing media onto a substrate. Typically, a large bias voltage is applied to a nozzle that is in fluid communication with a printing media reservoir. The electric field generated by the bias voltage draws the printing media through the nozzle and ejects it towards a substrate. Such printers are capable of printing high resolution features that are orders of magnitude smaller than printer nozzle size (e.g., inner diameter) [1]. Thus, EHD printers can be used during creation of a variety of devices, including, but not limited to, electronics (e.g., printed circuit boards), sensors (e.g., transmission fluid temperature sensors, and gas sensors), power modules, interconnects, biomedical devices (e.g., templates for cell growth), displays, actuators, energy harvesters, transistors, and organic light-emitting diodes (LEDs), just to name a few. The range of potential applications illustrate the usefulness of EHD printers in direct printing (e.g., sensors), front-end and back-end fabrication (e.g., transistors and PCBs, respectively), and packaging (e.g., interconnects).
EHD printing technology can also reduce cost and waste present in traditional microfabrication. For example, mask-based lithography, in general, is a microfabrication process used to create micro- or nano-scale patterns on a substrate and is commonly used to create integrated circuits. Typically, a light-sensitive chemical, also known as a photoresist, is deposited onto a substrate. An optical mask comprising a pattern can then be used to mask desired portions of the substrate. For example, in simpler proximity or contact systems, the optical mask is placed in close proximity to or in direct contact with the substrate. A specialized light source can then be used to expose the unmasked portions of the substrate, thus transferring the desired pattern to the substrate (e.g., by exposing unmasked portions of the light-sensitive photoresist). Traditional mask-based lithography can involve highly specialized equipment. For example, optical masks typically are constructed out of a fused quartz substrate layered with chromium, where the chromium layer is etched with a laser to create the desired masking pattern. Additionally, photoresists can comprise relatively expensive chemicals that are usually wasted (e.g., removed from the substrate and discarded) during the masked based lithography process. Current alternative methods for achieving similar results are electron beam lithography, which is time consuming and expensive, nano-imprint technology, which generally involves expensive molds made of specialized materials, and piezo-driven printing, which is typically limited to low viscosity printing materials (e.g., with a viscosity less than 50 centipoise (cP)) and thus can require multiple superimposed printing runs when printing thicker structures and offers a relatively low printed feature resolution.